Re: [PATCH] Export explicit instantiations for C++17 members of std::string

[Jonathan Wakely <jwakely at redhat dot com>]

On 06/01/19 17:18 +0000, Jonathan Wakely wrote:
> On 06/01/19 17:59 +0100, Rainer Orth wrote:
> > Hi Jonathan,
> >
> > > The C++17 standard added some new members to std::basic_string, which
> > > were not previously instantiated in the library. This meant that the
> > > extern template declarations had to be disabled for C++17 mode. With
> > > this patch the new members are instantiated in the library and so the
> > > explicit instantiation declarations can be used for C++17.
> > >
> > > The new members added by C++2a are still not exported, and so the
> > > explicit instantiation declarations are still disabled for C++2a.
> > >
> > > 	* config/abi/pre/gnu.ver (GLIBCXX_3.4.21): Make patterns less greedy
> > > 	for const member functions of std::basic_string.
> > > 	(GLIBCXX_3.4.26): Export member functions of std::basic_string added
> > > 	in C++17.
> > > 	* include/bits/basic_string.h (basic_string(__sv_wrapper, const A&)):
> > > 	Make non-standard constructor private.
> > > 	[!_GLIBCXX_USE_CXX11_ABI] (basic_string(__sv_wrapper, const A&)):
> > > 	Likewise.
> > > 	* include/bits/basic_string.tcc (std::string, std::wstring): Declare
> > > 	explicit instantiations for C++17 as well as earlier dialects.
> > > 	* src/c++17/Makefile.am: Add new source files.
> > > 	* src/c++17/Makefile.in: Regenerate.
> > > 	* src/c++17/cow-string-inst.cc: New file defining explicit
> > > 	instantiations for basic_string member functions added in C++17.
> > > 	* src/c++17/string-inst.cc: Likewise.
> > >
> > > Tested powerpc64le-linux, committed to trunk.
> >
> > this patch broke Solaris bootstrap:
> >
> > ld: fatal: libstdc++-symbols.ver-sun: 6705: symbol 'std::basic_string<char, std::char_traits<char>, std::allocator<char> >::operator std::basic_string_view<char, std::char_traits<char> >() const': symbol version conflict
> > ld: fatal: libstdc++-symbols.ver-sun: 6707: symbol 'std::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >::operator std::basic_string_view<wchar_t, std::char_traits<wchar_t> >() const': symbol version conflict
> > ld: fatal: libstdc++-symbols.ver-sun: 6712: symbol 'std::basic_string<char, std::char_traits<char>, std::allocator<char> >::data()': symbol version conflict
> > ld: fatal: libstdc++-symbols.ver-sun: 6714: symbol 'std::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >::data()': symbol version conflict
> > ld: fatal: libstdc++-symbols.ver-sun: 6723: symbol 'std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::_S_to_string_view(std::basic_string_view<char, std::char_traits<char> >)': symbol version conflict
> > ld: fatal: libstdc++-symbols.ver-sun: 6724: symbol 'std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >::_S_to_string_view(std::basic_string_view<wchar_t, std::char_traits<wchar_t> >)': symbol version conflict
> > collect2: error: ld returned 1 exit status
> > make[6]: *** [Makefile:696: libstdc++.la] Error 1
>
> Sorry :-(
>
> [...]
>
> > The following patch allowed the build to finish.
>
> OK for trunk, thanks.
>
> I'll make sure to run my script to check for such conflicts before
> adding any more symbols.


The good news is that even with my soon-to-be-committed changes, I
only see the same problems you already found:

Symbol matches more than one version:
_ZNKSbIwSt11char_traitsIwESaIwEEcvSt17basic_string_viewIwS0_EEv
std::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >::operator std::basic_string_view<wchar_t, std::char_traits<wchar_t> >() const
 GLIBCXX_3.4        _ZNKSbIwSt11char_traitsIwESaIwEE[a-z]* (line 327)
 GLIBCXX_3.4.26     _ZNKSbIwSt11char_traitsIwESaIwEEcvSt17basic_string_viewIwS0_EEv (line 2098)

Symbol matches more than one version:
_ZNKSscvSt17basic_string_viewIcSt11char_traitsIcEEEv
std::basic_string<char, std::char_traits<char>, std::allocator<char> >::operator std::basic_string_view<char, std::char_traits<char> >() const
 GLIBCXX_3.4        _ZNKSs[a-z]* (line 261)
 GLIBCXX_3.4.26     _ZNKSscvSt17basic_string_viewIcSt11char_traitsIcEEEv (line 2097)

Symbol matches more than one version:
_ZNSbIwSt11char_traitsIwESaIwEE4dataEv
std::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >::data()
 GLIBCXX_3.4        _ZNSbIwSt11char_traitsIwESaIwEE[0-58-9][c-e]* (line 287)
 GLIBCXX_3.4.26     _ZNSbIwSt11char_traitsIwESaIwEE4dataEv (line 2102)

Symbol matches more than one version:
_ZNSs4dataEv
std::basic_string<char, std::char_traits<char>, std::allocator<char> >::data()
 GLIBCXX_3.4        _ZNSs[0-58-9][c-e]* (line 220)
 GLIBCXX_3.4.26     _ZNSs4dataEv (line 2101)

Symbol matches more than one version:
_ZNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEE17_S_to_string_viewESt17basic_string_viewIcS2_E
std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::_S_to_string_view(std::basic_string_view<char, std::char_traits<char> >)
 GLIBCXX_3.4.21     _ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EE1[5-9]* (line 1720)
 GLIBCXX_3.4.26     _ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EE17_S_to_string_viewESt17basic_string_viewI[cw]S2_E (line 2107)

Symbol matches more than one version:
_ZNSt7__cxx1112basic_stringIwSt11char_traitsIwESaIwEE17_S_to_string_viewESt17basic_string_viewIwS2_E
std::__cxx11::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >::_S_to_string_view(std::basic_string_view<wchar_t, std::char_traits<wchar_t> >)
 GLIBCXX_3.4.21     _ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EE1[5-9]* (line 1720)
 GLIBCXX_3.4.26     _ZNSt7__cxx1112basic_stringI[cw]St11char_traitsI[cw]ESaI[cw]EE17_S_to_string_viewESt17basic_string_viewI[cw]S2_E (line 2107)